A typical eddy-current sensor used to measure a position of an electrically-conductive object includes a cylindrical coil wound with a very fine magnet wire and energized with a high frequency alternating current. When a conductive object is placed in the proximity of such a coil, the alternating magnetic field produced by the current in the coil, induces eddy currents in the object, which change the impedance of the coil. This change in impedance depends on the distance between the object and the coil, and, therefore, can be used as a raw measure of the object position.
One of the applications of the position sensors is in Active Magnetic Bearing (AMB) Systems where they may be used to support rotors of rotating machines without mechanical contact in conjunctions with electromagnetic actuators and control systems. Position sensors in an AMB may constantly monitor the position of the rotor with respect to a stator and send information about the rotor position to a control system. Based on this information, the control system may apply electrical control currents to electromagnetic actuators, which may generate forces necessary to keep the rotor in the desired position without mechanical contact.